Elevated levels of the radioactive element iodine-131 that were detected in several nations have been identified as likely originating at a Hungarian research institute, nuclear authorities said Thursday.

Hungarian officials said the leak probably came from the Budapest-based Institute of Isotopes, the International Atomic Energy Agency said in a statement.

The institute has acknowledged emitting higher quantities of iodine-131 than normal but denies being the source of any elevated radiation.

“Radiation levels in Hungary were only a little higher in Budapest than elsewhere,” said Institute of Isotopes director Mihaly Lakatos.